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I am seeking some expert advice before I embark on a repair. 

I have a 2000s Gibson j45. The action is high about .120 There is saddle life but I fear if I take the saddle low enough to have comfortable action there wont be good string break angle because of the way this bridge was designed. The bridge pin holes are very far back which creates a long low string break angle

This is my question:

How much belly is expected to be on a Gibson of this era? Can someone give me a measurement using a straight edge parallel behind the bridge?

I thought i remember reading the radius is about 30"? but I am not sure exactly where to measure that radius. Directly behind the bridge?


It appears to me there is a significant belly. With a straight edge behind the bridge there is 3/16s" from the top to the straightedge on both the E and the e side. 

Ill get a picture up as soon as I can

I planned on using the Thompson belly reducer, but after thinking about it I wanted to get some incite as to how much belly is normal on these Gibsons. 

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Here are some photos. It looks like the gap on each side is about 1/8”
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Luke, I will say this looks horrid. Others with more experience than me will hop in. It does look to me like something is seriously wrong under the top.

Hey Kerry. So I did some digging and maybe this is normal. It is a uniform radius it appears that gradually and uniformly decreases the further out it goes.

There is nothing Lois under the top, everything is tight. I checked with a feeler gauge. I was told there is approx a 30” radius on the top which is about 1/8” when a straight edge is laid across the the top and measured at the binding.

I shaved the saddle down a bit and got the action down to .090 I would like it a little lower but I’m nervous about the string break angle and I don’t want to file groves into the bridge.

The neck is pretty flat .004 relief.

Wow. What do I know?

Thanks Bucko.

I don’t know Kerry. You could be right. One thing I am certain of is I don’t know! At this point I am so curious I may search out some used 2000s j45s and measure them.

I am perplexed. I’ll have to check out some Gibson forums on Facebook and see if anyone could give me some measurements.

I initially thought the top was significantly “bellyed” as your gut told you too. I was ready to put the belly reducer in there but then I thought I should ask only because the belly was so uniform...

Id check the neck block also , some taper away and have almost no contact with the back , which seems to allow a shift in neck angle .

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